This invention relates to a scale indication device for electronic components. More particularly, the invention relates to a driving mechanism and a character plate for changing the indicated scale on a meter of an electronic component such as a timer.
Examples of existing scale indication devices are found in the Japanese Official Bulletin for utility model (Kokai kooho) No. Heisei 2-7838, and the Japanese Bulletin for patent (Kokai kokho) No. Showa 63-10819.
The device described in 2-7838 is illustrated in prior art FIGS. 7 and 8. As shown therein, six sets of numerals 2 for time display, each consisting of four numerals, are printed on one side of display gear 1, which consists of a doughnut-shaped plate. The display gear 1 is rotatable about its axis, which is also the axis of dial 8, by gear 3. This causes the time display numerals 2 to appear sequentially in display window 6a, which is one of the display windows 6 in scale panel 5 on the face of timer 4. For example, the numerals might appear in the sequence "8, ""4,""0.8,""0.4." In other words, the rotation of gear 1 causes the numerals on the scale to change. Gear 7 is the input gear which causes display gear 1 to rotate.
In the existing timer described above, every part of the aforementioned display gear I rotates concentrically around the shaft of dial 8. As a result, all the time display numerals 2 must be printed on a single circumference of a circle with the shaft at its center. Thus if the exterior dimensions of timer 4 are fixed, the time display numerals 2 will necessarily be small, and the numerals on the scale will be difficult to read.
Furthermore, in order that the time display numerals 2 correspond perfectly to each of the display windows 6 on scale plate 5, they must be printed at a slight inclination which matches the angle of rotation of display gear 1. This requires a large amount of time and labor in the design phase and in quality control since it necessitates a high degree of accuracy in the printing of the time display numerals 2.
The device described in 63-10819 overcomes the problem of size and inclination of the characters by using an extremely complex gear system to move the character plate in a non-concentric fashion. In addition to increasing the cost due to the large number of parts, the 63-10819 device requires "two-sided" assembly (i.e., the gear system requires assembly from both the front and the rear), thus requiring that the device be fully assembled prior to connection to other components. This is a disadvantage as it may be desirable to assemble the scale indication device from only the front side after the back portion has been attached, for instance, to a circuit board.